1. Field of the Invention
The present invention relates to a system and a method for communication using an IP (Internet Protocol), and more particularly to a system and a method for communicating by using different IPs according to a specific service by a UE.
2. Description of the Related Art
As generally known in the art, an IP refers to an Internet layer protocol devised to provide wired communication devices with various types of packet services. Development of IP communication technology is followed by discussion of schemes for allocating an IP to a UE to support a packet service in a mobile communication system.
An IP allocated to a UE is maintained the same in a subnet managed by a gateway that has allocated the IP. However, if the UE moves or if the gateway is changed by a specific communication situation, a new IP is generally allocated to the UE by a new gateway. Then, the service that has been provided through the previous IP is interrupted or terminated.
In other words, use of a fixed IP has a problem in that the continuity of the service provided to the UE is not generally guaranteed if the UE moves or if the communication situation of the UE varies.
This will be explained with reference to an example. It is assumed that a UE supports a VoIP (Voice of Internet Protocol) service by using an IP. The UE supports voice communication with another UE by using an allocated IP. If the user moves (e.g. by mass transportation, by car, or on foot), the gateway of the IP allocated to the UE may move out of the area under management. In this case, the UE is assigned a new IP from a new gateway. This means, in this situation, the UE cannot support the VoIP service any more by using the previously allocated IP.
As a result, the voice communication between both UEs is interrupted, and the UE must dial again, i.e., the voice communication-related call setup signaling must resume from the beginning.
In an attempt to solve the above-mentioned problem, a mobile IP has been proposed. According to this scheme, a UE is assigned two IPs, i.e. a fixed IP that remains unchanged regardless of mobility of the UE, and a mobile IP that varies as the UE moves. The fixed IP is referred to as a HA (Home Address), which is made known to the outside when the UE is to use a service. The mobile IP is referred to as a CoA (Care of Address).
When the mobile IP is applied to a UE supporting the VoIP service, the UE has a HA and a CoA. If the UE moves, the CoA is varied, but the HoA is retained, so that the voice communication service is maintained continuously.
As explained above, a specific service in a communication system must have its continuity guaranteed, considering the service characteristics. This is crucial for satisfying the demand of service users. The specific service includes, for example, a VoIP service, a FTP (File Transfer Protocol) service, a streaming service, etc.
The service continuity is becoming a major issue in the next-generation mobile communication system, and the mobile IP needs to be adopted in connection with support for the service continuity. This necessitates discussion of a detailed method regarding how and which IP is to be used for communication in connection with service continuity in the next-generation mobile communication system.